Cannibalizing Harmonia axyridis (Coleoptera : Coccinellidae) larvae use endogenous cues to avoid eating relatives

Cannibalism is widespread among many different organisms, and can have bath negative and positive fitness consequences. Avoiding eating relatives can minimize negative fitness consequences of cannibalism Such avoidance requir es kin discrimination; but evidence for this ability among cannibals is Lim ited with little data that address the cues used in such discrimination. We examined whether larvae of the ladybird beetle Harmonia axyridis avoid eat ing their relatives. We further manipulated environmental factors to.,creat e individuals that had similar or dissimilar rearing environments to begin to test for endogenous versus exogenous recognition cues. Zn our experiment s, third-instar larvae were much less likely to cannibalize if they were in teracting with a relative. Larvae; that did cannibalize kin required more:e ncounters, and significantly delayed cannibalism, compared to larvae cannib alizing unrelated individuals. Acquired cues were less important. Even thou gh the different rearing environment resulted in: significantly different p henotypic effects, similarity or dissimilarity of, rearing environment had no effect on cannibalism, and there was no interaction between environments and relatedness in cannibalism. We suggest that H. axyridis has a well-dev eloped kin discrimination system, and that kin recognition in this ladybird beetle is based on endogenous rather than exogenous cues. We also argue th at these cues reflect either direct or indirect genetic effects on larval p henotypes.